1. Field of the Invention
The present invention relates to a method of mechanized construction for earth wire under-bracing for supporting and stabilizing a utility pole, and more particularly to a device and method of mechanized construction for earth wire under-bracing, in which the burial hole for a large-sized earth wire under-bracing can be dug by mounting an extendable excavating unit at the lower end of the auger. A burial hole is constructed for both small-sized and large-sized under-bracing by using the same extendable excavating unit with an auger crane.
2. Description of the Related Prior Art
Generally, in the construction of electrical power transmission and distribution lines and communication lines, if a utility pole is installed and wire and communication cables are strung, earth wires for reinforcing against unbalanced tensile forces of the wires and communication cables are installed, so as to prevent the utility pole from leaning or falling over.
When the earth wire is installed, the excavation work for burying the earth wire under-bracing is first performed by manual labor or machine, and then the earth wire under-bracing is buried in the excavation to be connected by earth wire to the utility pole.
In order to bury such earth wire under-bracing, a burial hole having a predetermined depth should be dug at a spot where the earth wire under-bracing is to be buried. However, where the burial hole is dug by manual labor, it is problematic in that an unnecessarily large burial hole must be dug in order to make sufficient space in the hole for the workers to dig.
As a result, the soil around the excavation site is weakened, thereby relatively degrading the supporting force of the buried earth wire under-bracing when the burial hole is back-filled.
Further, to compensate for the above problem, a vertical excavation hole is dug by using an auger crane, and then an earth wire under-bracing rod is buried and back-filled. However, in the conventional mechanized excavation method, the earth wire rod providing the under-bracing is not at a right angle with the earth wire. Thus, tensile force is generated in the earth wire rod and the under-bracing is lifted out of the ground, allowing the utility pole to lean. This method may cause shoddy and faulty construction.
The under-bracing is commonly made of rectangular blocks, and at the time of construction, the under-bracing is buried horizontally with respect to the utility pole. However, the most ideal construction method is to fasten the under-bracing and the earth wire rod to the utility pole at a right angle.
But, as described above, manual labor leads to excessive labor costs and prolongs the construction time, and the mechanized excavation causes shoddy and faulty construction and weakens the burial supporting force of the under-bracing.
Furthermore, as described above, there is difficulty at many sites, in having to dig a hole in order to bury under-bracing of a rectangular block shape.
Accordingly, Korean Patent Application No. 2005-095892 filed by the applicant of the present invention discloses a mechanized construction method for earth wire under-bracing, in which a burial hole is dug in such a manner that a sloped excavation is dug by an auger crane, or an initial sloped excavation and a second vertical excavation are carried out by stages according to the type of soil. Then earth wire under-bracing of an optimum size is inserted and buried in the hole, and an earth wire rod connected to the earth wire under-bracing is connected to the vertically raised utility pole.
According to the mechanized construction method for earth wire under-bracing for utility poles and the round earth wire under-bracing applied thereto which are disclosed in the aforementioned patent application, the simplification of an excavation process can lead to a reduction in the number of workers and a decrease in working hours. Also, the right angle state between the earth wire rod and the earth wire under-bracing is stably maintained, thereby sharply increasing the supporting force and overcoming problems such as leaning of the utility pole and shoddy and faulty construction. Further, the work environment is improved, keeping people from being angered by inconvenience in traffic, and the construction quality is improved, because it offers excellent protection from natural disasters by providing a firm supporting force, thereby smoothly and reliably supplying high quality power.
The earth wire under-bracing applied to the method disclosed in the aforementioned patent application is a round block when viewed from above, and there are two sizes of earth wire under-bracing, one having a diameter of 43 cm with tolerance: ±5% that is referred to as a small-sized under-bracing, and the other diameter of 62 cm with tolerance: ±5% that is referred to as a large-sized under-bracing. If necessary, a medium-sized under-bracing, which is substituted for 1.0 M conventional under-bracing, can be manufactured and used. The difference in the diameter between the two earth wire under-bracings is determined by considering the variables of the target installation.
The earth wire under-bracings having the aforementioned diameters are for substitution of conventional earth wire under-bracing having rectangular block shapes. The conventional rectangular earth wire under-bracings have lengths of 0.7 M, 1.0 M, and 1.2 M.
In order to bury the earth wire under-bracing manufactured in a round shape, a burial hole having a predetermined inner diameter has to be excavated by using an auger crane. The excavation diameter of an existing auger crane is limited to 50 cm, so using an existing auger crane, it is possible to bury a small-sized under-bracing (43 cm) that is manufactured as a substitute for a 0.7 M earth wire under-bracing, but impossible to perform a mechanized construction of a large-sized under-bracing (62 cm) that is manufactured as a substitute for 1.0 M and 1.2 M earth wire under-bracings.
Therefore, in order to bury a large-sized earth wire under-bracing having a diameter of 62 cm, excessive labor hours are consumed by manual labor excavation, so it is very uneconomical. Further, the construction quality and the construction techniques are not standardized, thereby sharply degrading the working efficiency.